In the installation of temporary dust partitions, for example of the type disclosed in U.S. Pat. No. 5,924,469, U.S. Ser. No. 10/600,939, filed Jun. 20, 2003, U.S. Ser. No. 10/600,300, filed Jun. 20, 2003, and U.S. Ser. No. 11/125,583, filed May 10, 2005 the contents of each being incorporated herein by reference, a plastic sheet of material, or other type of material sheeting, is installed between a ceiling and a floor of a room to isolate or seal portions of a room from airborne dust or fumes.
In such partition installations, especially in longer-term installations, it has become popular to apply a zippered opening in the plastic sheeting, to allow for rapid entry and exit to and from the partitioned area. Examples of zippers of this type are disclosed in U.S. Pat. No. 5,819,474, 5,067,207 and 5,311,648, the contents of each being incorporated herein by reference. Such zippers commonly include left and right teeth portions, that are respectively bound to left and right flanges. The left and right teeth portions are opened and closed using a zipper pull. The left and right flanges in turn have an adhesive backing that is applied to the installed plastic sheeting.
During installation of a zipper opening of this type, the adhesive backing of the zipper is applied to the plastic sheeting at the location where the zipper is to be installed. The zipper pull is then engaged to open the left and right zipper teeth on the zipper. This exposes the underlying plastic which is still taut and uniform under the zipper. A knife, such as a box cutter, is used to pierce and cut the plastic that is framed by the left and right flanges of the zipper. The plastic is cut for the entire length of the zipper, leaving behind an opening that can be used as an entryway for the installation. The entryway can be opened and closed at will by engaging and releasing the zipper.
When the plastic sheeting underlying the zipper teeth is cut in this manner, a flap of plastic material remains on either, or both, sides of the opening. The flap is usually non-uniform in width, as the knife, when cutting, can waver between the left and right sides of the opening, leaving a unsightly seam. In addition, the flap can interfere with the operation of the zipper, as it can become lodged, or otherwise snag, in the teeth of the zipper during closure. A box cutter also has an exposed razor blade that can be dangerous to operate.